(1) Field of the Invention
The invention is directed to a machine tool for incorporating gear teeth into the inner side of an annular workpiece, preferably by machining (or: metal cutting).
(2) Description of the Prior Art
The production of gear teeth on the inner side of annular objects is somewhat more difficult than the incorporation of external teeth on gear wheels or the like. In particular, various methods involving the use of a worm milling cutter for hobbing the surface to be provided with gear teeth are not possible. Rather, machining processes that are considered suitable for internal gear teeth are shaping or—in particular in the case of machining large rings—milling of the teeth by means of a milling cutter. In this case, the workpiece to be machined, still without teeth, is placed onto a table, for example in the form of a circular disk, and fixed there. The machine head is held over the inner space within the ring to be machined by means of an extension arm from a stand arranged alongside the table. By driving the machining tool—rotation of a milling head or reciprocating movement in the case of a shaping machine—one tooth after the other is incorporated, the table being turned further by an amount corresponding to the spacing between the teeth after the completion of a tooth. In the case of this procedure, the extension arm carrying the machining head represents a weak point, because the high cutting forces originating from the machining head can only be insufficiently absorbed by this extension arm and vibration of the arrangement is therefore unavoidable. Such vibration is extremely undesirable, however, because it results in inaccurate cuts.